Wire bonding is, at this time, the dominant method used for the interconnection of semiconductor-based devices. In the wire bonding industry, tool failure leads to the destruction of the semiconductor device being interconnected, which can significantly lower yields. To prevent tool failures, tools are exchanged regularly prior to the predicted time of failure.
The wire bonding process is defined by the “Process Window,” which is the range of parameters that the bonding machine is qualified to operate within. To maintain bond quality, adjustments must be made to the bonding parameters. Bonding parameters, however, are not allowed to be outside of the approved process window. This leads to a loss of productivity as the bonding process must be stopped and tools exchanged. Furthermore, additional expense is incurred as a larger number of tools than necessary are used.
Contamination build-up and accelerated wear limit the useable time for conventional ceramic-based tools (e.g. Alumina, Zirconia toughened Alumina, Zirconia, cemented Tungsten Carbide, etc.) in wire bonding applications. Adhesion of organic-derived carbonaceous material and the subsequent embedding in the carbonaceous material of metallic particles from the bonding wire causes unsymmetrical loading of the tool and eventually leads to mechanical failure of the bonding tool by flexural bending. The carbonaceous material is produced by the action of the Electric Flame Off (EFO, for ball formation) on the petroleum and stearate-based materials typically placed on the wire surface to improve de-spooling of the wire. Enhanced surface wear is also caused due to the localization of bonding forces to a point load on the tool face.
U.S. Pat. Nos. 5,871,141, 5,558,270, and 5,421,503 assigned to the same assignee as the present invention, describe various conventional bonding tools for producing wire bonds on semiconductor devices and are incorporated herein by reference.